Optical fibers typically have a glass core that is manufactured from a glass body, usually called a preform. Using a process known in the art as “drawing,” the glass preform is placed at the top of a fiber drawing tower where it is heated in a furnace to a temperature that is sufficiently high to soften a bottom portion of the preform where the softened material is stretched by a series of steps to form an optical fiber glass core. The glass core is generally surrounded by additional layers of glass having a refractive index lower than that of the core. These surrounding layers are generally referred to as cladding. The glass core and the surrounding cladding layers are typically referred to as “an optical waveguide.”
Over the cladding there are often two or more superimposed polymer layers that form a coating system. Usually, this coating system is applied directly onto the optical waveguide during the drawing process. The coating layers are in direct contact with the optical waveguide or glass core so that the coating system can help to absorb forces applied to the coated optical fiber. Subsequent losses associated with the coating layers provide protection against microbending that can lead to attenuation of the signal transmission capability of the coated optical glass fiber.
Improvements in the process for coating the optical waveguide and changes in the chemistry and resulting properties of the coating layers can have dramatic effects on the final optical fiber produced.